1. Field of the Invention
The present invention relates to a flexible circuit board having a wiring layer formed directly or through an adhesive on a surface of an insulating film, and also relates to a method for production thereof. More specifically, the invention relates to a flexible circuit board and a method for production thereof, in which the flexible circuit board can be processed into an arbitrary shape, and in which the flexible circuit board can be used for connection between component parts which are mounted on various kinds of electronic equipment such as communication and visual equipment, etc., as well as automotive vehicles, aircrafts, robots, etc., and used for a mounting circuit board with components mounted thereon, and for a filament part on which a plurality of LEDs (Light Emitting Diodes) are mounted thereon and which is mounted on a lighting device.
2. Description of Related Art
As a conventional circuit board, there has been already known an all-layer IVH resin multilayered circuit board as disclosed, for example, in Japanese patent application laid-open No. 2003-008161 (first patent document). In addition, there has also been known a so-called flexible circuit board which is used with the whole or a part thereof being bent, and in recent years, such a flexible circuit board is used for a liquid crystal driver module of a portable device, etc.
In FIG. 5, there are shown schematic cross sectional views of a typical flexible circuit board. As shown in FIG. 5A, a flexible circuit board 100 has a wiring layer 30 formed on an insulating film 20, and an insulating layer 40 (generally referred to as a cover lay layer (CL layer)) formed on the wiring layer 30. Moreover, as shown in FIG. 5B, there is also known a flexible circuit board which is formed of a plurality of these layers. As illustrated, a through hole 50 for electrically connecting individual wiring layers 30 to one another is formed in the multilayered flexible circuit board 100, so that complicated connections of wirings can be thereby made. In addition, the flexible circuit board 100 shown in FIG. 5A and FIG. 5B is in a form in which the wiring layer 30 is directly formed on the insulating film 20, but as another form, there is also known a flexible circuit board in which an adhesive layer is arranged between an insulating film and a wiring layer. Here, note that in the conventional flexible circuit board, polyimide films are used as the insulating film 20 and the insulating layer 40, respectively, and a rolled copper foil is used as the wiring layer 30.
The flexible circuit board having such a construction is thin and freely bendable, so that it can be inserted into a small space between component parts. As a result, many mounting components can be arranged even in the small space between the component parts, thus making it possible to improve packaging density in the space between the component parts. That is, with the use of the flexible circuit board in a bent state, it is possible to attain advancement in functionality and reduction in size of a device, and hence, in the future, the deployment of use thereof in still broader fields is expected. Here, note that related techniques are disclosed in the first through third patent documents, as listed below.